The physical geometry and dimensions of tunnel ovens which are adapted for air impingement food baking place restrictions upon acceptable locations within such ovens where their air blowers and air distributing plenums may be installed. Such ovens typically include a longitudinally extending food conveyor which passes through ports within the longitudinal end walls of the oven's baking case. Accordingly, the longitudinal ends of such ovens typically cannot serve as a mounting site for the oven's blower and air plenum. Space considerations further restrict blower and plenum mounting sites. Such tunnel ovens are typically compactly stacked, one over the other, in pairs or triples. In order to make such stacked tunnel ovens useable by average height persons, such ovens are designed to have a low vertical profile. The need for minimizing the vertical dimension of such ovens eliminates the spaces within such ovens which overlie and underlie the food conveyor as an acceptable location for installation of the oven's blower and air plenum.
The two remaining sites within such tunnel ovens which are candidates for installation of the plenum and blower are the oven's left and right or lateral and oppositely lateral sides. Typically, such oven's oppositely lateral side is configured as a removable access panel or door, making such side unsuitable for blower and plenum installation.
By the process of elimination, the sole remaining location within such tunnel ovens for air blower and plenum mounting is the oven's lateral side. While placement of a tunnel oven's air blower and plenum at its lateral side advantageously solves several design challenges (as described above), such lateral positioning creates other difficulties. For example, it is desirable that a tunnel oven provide a balanced flow of food impinging air across the lateral width of the oven's conveyor. Yet, placement of the oven's air blower and plenum at the oven's lateral side requires that air propelled by the blower be initially directed toward the oven's oppositely lateral side. Such oppositely lateral direction of impingement air creates a relatively high air pressure zone at the oppositely lateral side of the oven's baking chamber, and creates a corresponding relatively low air pressure zone at the oven chamber's lateral side.
In order to counteract such lateral air pressure imbalances, within a tunnel oven's baking chamber, duct work extending within the chamber (commonly configured as a longitudinally arrayed series of oppositely laterally extending air duct “fingers”) is commonly volumetrically tapered, such air ducts having their larger volume at their lateral ends, and having their smaller volume end at their oppositely lateral ends. However, air flow modifications to such duct work commonly fails to achieve true air pressure equilibrium across the lateral width of the oven's baking chamber. Finger ducts which are modified to sufficiently evenly dispense air across the lateral width of the oven's conveyor often undesirably leave a residual air pressure imbalance between the lateral and oppositely lateral sides of the baking chamber.
Such residual air pressure imbalances tend to create undesirable air flow patterns at the oven's food passage ports which open the oven's longitudinal and oppositely longitudinal ends. Typically, such food passage ports are oblongated, the orientation of their long axes matching the general lateral progression of the gradient of the above described undesirable residual air pressure imbalance. Accordingly, just as the above described typical tunnel oven produces a residual air pressure imbalance between the lateral and oppositely lateral sides of its baking chamber, air pressure imbalances tend to exist between the lateral and oppositely laterally ends of the oven's oblongated food passage ports. Such air pressure imbalances at such ports create counter-rotating air vortices at the food passage ports, such vortices undesirably expelling hot cooking air at the oppositely lateral ends of the food passage ports, and commensurately undesirably aspirating room temperature air at the lateral ends of the food passage ports. Circulation of such air vortices markedly reduces both the cooking efficiency and energy efficiency of the tunnel oven.
The instant invention solves or ameliorates defects, drawbacks, and deficiencies discussed above by providing a tunnel oven which incorporates means for creating a vortex disrupting opposing “air curtain” at the lateral ends of the oven's food passage ports.